Systems have been developed to obtain an auditory evoked response (AER) or brainstem auditory evoked response (BAER) from a patient that represents activity of the patient's auditory system. The AER is an electrical brain wave or neural response obtained from electrodes placed on the patient in response to a stimulus, normally a sound. Depending on the latency of the response and the placement of the electrodes, different classes or types of AERs can be obtained. Those with the shortest latency are generated by the inner ear and the auditory nerve, and are referred to as electrocochleography (“ECOG” or “ECochG”) responses. The next response reflects activity within the auditory brainstem and is referred to as an auditory brainstem response (ABR). Further detail is provided in Hall, James W, III; Handbook of Auditory Evoked Responses; Allyn and Bacon; Needham Heights, Mass., 1992.
Electrocochleography systems are currently used to perform diagnoses of the cochlea and vestibular apparatus. In the case of the vestibular system, recently analysis for this specific part of the ear has been referred to as electrovestibulography (EVestG), being a distinct variant of ECOG. The systems are used to produce a patient neural response which involves placing a recording electrode as close as practical to a patient's cochlea. An acoustic transducer, eg an earphone, can be used to provide an auditory stimulus to evoke the response. For EVestG the patient can be tilted, in different directions, to evoke a specific response from the otoacoustic apparatus, but predominantly the vestibular apparatus. It is not necessary to also use an auditory stimulus for EVestG. A distinct EVestG signal, similar to an ECOG signal but representing the neural response from the predominantly vestibular apparatus, is used to determine an Sp/Ap ratio that can be used for the diagnosis of a number of conditions, particularly Meniere's disease. The first wave, normally labelled N1, of the response signal is examined to determine the summating potential (Sp), the action potential (Ap) and the second summating potential (Sp2), as shown in FIG. 1. The response is only of the order of a few μV and is received with considerable unwanted noise making it difficult to determine and isolate.
International Patent Publication WO 2006/024102 by Monash University describes an ECOG system to extract neural event data that can be used to indicate whether a person has Meniere's, Parkinson's disease or depression. The system produces biological marker data representing the Sp/Ap ratio and a TAP marker that can be used to indicate the presence of a disorder.
International Patent Publication WO 2008/144840, also by Monash University, describes a neural response system for generating biomarker data representing a number of biomarkers for time segments associated with filtered electrovestibulography response signals.
To assist with identification of a wide variety of neurological and neurodegenerative disorders, particularly those associated with the central nervous system (CNS), it would be advantageous to provide at least a useful alternative or in particular an improved system that is able to analyse the neural event data and the biological marker data and produce displays or plots which are able to clearly correlate distinctions in the data obtained to indicate the presence or absence of a condition or disorder in a patient.